The primary objective of this study was to establish sedimentary models for peat formation in the southern part of the Klip River coalfield during Ecca (Permian) times and to assess palaeoenvironmental controls on coal seam behaviour and distribution. In order to achieve this approximately 2 400 borehole logs and 25 field sections were collected. The coal-bearing Vryheid Formation records early to late Permian fluvio-deltaic sedimentation within the northeastern main Karoo basin. Three informal lithostratigraphic subdivisions, based on the investigations of Blignaut and Furter (1940, 1952), are proposed: the Lower zone, Coal zone and Upper zone. An examination of the structural framework and history of the northeastern Karoo basin reveals that the southern and western boundaries of the Klip River coalfield are defined by zones of rapid basement subsidence : the Tugela and Oannhauser Troughs respectively. There is some doubt as to the locality of the source area to the rivers emptying into the Ecca sea. Ryan (1967) postulated the "Eastern Highlands" situated off the present southeast African coast, but it is contended that the Swaziland area, situated no more than 200 to 300 km to the northeast of the Klip River coalfield, constituted a more plausible source area. The Lower zone represents sedimentation along a westerly to southeasterly prograding coastline dominated by high-constructive lobate or braid deltas, but also showing significant influence by wave processes. The Coal zone, which varies in thickness from 35 to 60 m, represents a major phase of coastal progradation and braided-river deposition on extensive alluvial plains. Significant coal seams formed only during periods of fluvial inactivity, the duration of which was dependent on source-area processes. Coal seam geometry and behaviour in the Klip River coalfield were not influenced by the depositional environments of associated clastic sediments. The following factors were found to have of profound influence in determining the extent, distribution and rate of peat accumulation: 1. Platform stability and temporal and spatial variations therein. 2. The absence or presence of penecontemporaneous clastic sedimentation. 3. Duration of periods of peat formation. 4. Lithology and topographic expression of clastic sediments underlying peat-forming swamps. The peat-forming phase of the Vryheid Formation was terminated by an extensive transgression brought about by an eustatic rise in basin water-level and/or an increased rate of platform subsidence. / Thesis (Ph.D.)-University of Natal, 1988.

Permeability is that physical property of a porous medium that controls the flow of fluids through that medium. The flow of methane and water may be induced by the excavation of a mine opening in methane-bearing strata. Methane flow into a mine opening constitutes one of the biggest hazards in the coal mining industry. It is poisonous to humans and can ignite at concentrations as low as 5 % per volume and create explosions in the presence of coal dust from mining. If the flow of methane and/or water into the mine opening becomes blocked by an impervious layer, excessive pressures may develop, particularly in the roof strata of the mined seam, which can lead to roof falls. In order to characterize the flow of methane and water into and around the openings in a mine, that was plagued by roof falls suspected of being the result of excessive fluid pressure build-up, a large scale laboratory investigation of the permeability of the roof sediments of the working coal seam in the area was undertaken. The permeability was measured under atmospheric conditions by means of a modified Ohle permeameter, and under triaxial conditions with the aid of a modified Hoek cell. The permeability of the sediments towards methane and water was measured. Nitrogen was used as a control because it is much less reactive than methane towards the sediments used in this project. It was found that the permeability decreases with increasing gas pressure, in the case of gas being the permeating fluid, and increased with increasing water pressure, in the case of water being the permeating fluid. In some instances anomalous plots of permeability versus reciprocal mean gas pressure were obtained. These were attributed to the effects of methane adsorption or the Klinkenberg effect, and a possible method to determine which of the two processes is dominant is discussed. To characterize the flow in the roof strata of the coal seam being mined, the permeability was correlated to fades type. The different fades types were numbered from 1 to 14 with increasing grain size for ease of correlation. Due to the variable nature of the sediments, even in a fades type, no single permeability could be obtained for a fades type. Instead permeability ranges were obtained for each fades type. The definition of the lower and upper limits for each range were found to be dependant on the number of tests done on samples for that fades type. Nonetheless a relationship of increasing permeability with increasing grain size was found in the coarser grained fades (facies type 8 and higher). For the fIner grained fades types the permeability was found to decrease with increase in grain size. A graph could be constructed for use in predicting possible hazardous zones by identifying the fades type and then reading the permeability range that can be expected off the graph. Due to the variable nature of the sediments, the graph is, at this time, only applicable to the areas where the samples were obtained. A permeability prediction graph for all localities would be an ideal but is beyond the scope of this project. Such a graph, and the methods discussed have a wide range of applications in the coal mining and methane gas exploitation industries. / Thesis (M.Sc.)-University of Natal, Durban, 1994.

D.Phil. (Geology) / Please refer to full text to view abstract

M.Sc. / The study site for this project is New Clydesdale Colliery situated in the Witbank Coalfield, South Africa. The Witbank Coalfield is located within the northern part of the Karoo Basin where the major coal deposits in South Africa are located. Optimum ash fusion temperatures derived from coal in this region are approximately 1400°C, and higher, although temperatures above 1300°C are also acceptable. In certain coal seams the ash fusion temperatures drop well below this optimum temperature, leading at times to problems in the user industry. Ash fusion temperature which is the temperature at which the mineral matter in coal begins to soften, flow and fuse, is an important aspect relating to coal utilization but is little understood and under-studied in South Africa. The objective of this thesis is to attempt to determine what factors, mineralogical or inorganic chemical, influence variations in the ash fusion temperatures in certain coal samples. An understanding of this problem will have a bearing on the ultimate assessment of a coal for utilization purposes, in general, and ash deposition prediction in future boiler plants in particular. This study is somewhat pioneering as no detailed studies have been undertaken or published previously. Samples were collected at four sites from New Clydesdale Colliery. The sample sites were selected based on pre-existing knowledge of the ash fusion temperatures obtained from company analytical sheets. The sites were therefore representative of low and high ash fusion temperature coal. The first two sites were located in the opencast area where the No. 2 seam is actively being mined. The other two sites were located underground where mining has ceased. Conventional analyses conducted on the samples include proximate analyses, calorific values, percentage sulphur, and ash fusion temperatures. Further analyses performed included ash analyses (composition of ash), X-ray diffraction, scanning electron microscopy and petrographic studies. It was found that although complex relationships exist between ash fusion temperature and the various geological and coal parameters, positive results were obtained. These indicate a possible relationship between low ash fusion temperatures and i) finer size fractions, ii) an increase in iron content present in the form of pyrite and iii) the form in which pyrite is present, namely cleats. High ash fusion temperatures tend to correlate with i) the absence of pyrite or ii) pyrite present as framboids.

No description available.

This study was carried out on the main coal-producing and the extensively block-faulted area of Mchenga Coal Mine, southeast of the 90 km2 intracratonic Livingstonia Coalfield in the north of Malawi. It was initiated against the background of indistinct information on coal geology, shortage of energy and potential environmental threats due to mine activities. The study aimed at integrating investigations of characterization of the lithostratigraphy, coal seam correlation, coal quality determination, examination of the mineralogy and geochemistry of coal and hosts rocks, assessment of water quality and providing information for mining and potential environmental and water quality impact assessment in the study area. The methodologies used in this study include literature review, field visits, mapping, sites selection and characterization, borehole logging, geochemical analyses, data processing and interpretation. The geochemical analyses include proximity analysis of coal quality, microscopy and X-ray Diffraction for mineralogy and petrology, X-ray Fluorescence (XRF) for rock geochemistry and Atomic Absorption Spectrometry for determination water geochemistry. The results have shown that a) The Coal Measures comprises of four to six coal seams in different localities, and the occurrence is flat and gently dipping southeast and are correlated. Thicknesses of the coal seams vary from 0.10m to 3.0m with some notable lateral and horizontal variations. Thick and workable seams occupy the lower portion of the Coal Measures and are exposed along the North Rumphi River bank; b) Coal quality belongs to sub-bituminous ‘A’ to ‘C’ on ASTM classification (1991), being characterised by low moisture content (0.8 to 1.3 wt percent) and sulphur content (0.49 to 0.85 wt percent), high ash content (9.0 to 17 wt percent) and volatile matter (24 to 32.9 wt percent), fixed carbon (53.6 to 62.6 wt percent), calorific value (7,015 to 7,670 kcal/kg); c) Mineral matters constitute approximately 9.55 to 38.34 wt percent of the coal samples, predominantly clays (interstratified illite/smectite and kaolinite) with varying proportions of quartz, mica and feldspars, as well as minor calcite and pyrite and their geochemistry, being characterised by enrichment of SiO2 from 5.37 to 20.56 wt percent, Al2O3 (2.63 to 11.21 wt percent) and K2O (0.32 to 3.65 wt percent) with trace concentrations of CaO (0.04 to 0.41 wt. percent), MgO (0.08 to 0.65 wt percent) and P2O5 (0.018 to 0.037 wt percent) and Na2O concentration notably below 0.01 wt percent; d) Calcite and pyrite constitute minor concentration in both sandstones and shales; e) Water quality in the area is characterised as two groups of acidic (pH 3.3-6.4) and near-neutral to slightly alkaline (pH 6.9-7.3) and low pH, high TDS, SO42- and EC are noted at the coal crusher plant which points out to high leaching of trace elements such as Pb and Fe. Na++K+ are dominant in upper sections of North Rumphi and Mhlepa Rivers. Ca2+ cations are dominant at crusher plant, underground mine and lower section of Mhlepa; f) Based on the geochemistry analysis, Na and trace elements such as Ti, V, Mn, Fe, Zn, Rb, Sr and Zr from coal and host rocks have the ability to contribute significantly to deterioration in the ground and surface water quality in the study area. It can be concluded that the coals of the Livingstonia Coalfield belong to Gondwana group deposited in sub-basin with multiple seams embedded in sandstone and shale host rocks.

The coal-bearing sediments of the Antelope coal field in the southcentral Powder River Basin, Wyoming were deposited in paludal and tributary subsystems of the fluvial system that existed in the basin during the early Tertiary. A depositional model for the Antelope coal field was constructed from data collected from approximately 500 drill holes that penetrated the upper 90 meters (300 feet) of the Fort Union Formation. The depositional environments were interpreted from lithologic descriptions and guidelines established in the literature. The two main coal seams at the Antelope coal field are the Anderson and stratigraphically lower Canyon coal seams. They represent poorly-drained swamp depositional environments. Each of the coal seams exhibit splits into multiple and thinner coal seams to the southwest. The parting rocks that lie between these splits, sedimentary structures, and isopach maps of the partings indicate that crevasse splaying with lacustrine and small channel development caused the observed splits in the coal seams. Distal overbank deposits occur at the top of the Canyon seam and at the base of the Anderson seam; well-drained swamp deposits and crevasse splay, lacustrine, lacustrine delta, and small channel-fill deposits occur in between the coal seams. The rocks underlying the Canyon coal seam suggest that the area of the Antelope coal field was a poorly-drained swamp that developed into a well-drained swamp with minor small channel development. The area once again digressed to a poorly-drained swamp which was the beginning of the Canyon coal swamp. The rocks overlying the Anderson seam represent a combination of the environments mentioned above with deposits from lacustrine and well-drained swamp environments dominating. The observed splits in the Anderson and Canyon coal seams to the southwest at the Antelope coal field suggest that a change in the fluvial system and/or tectonic stability of the Powder River Basin occurred and affected deposition in the southcentral portion of the basin. A combination of 1) relative basin subsidence, 2) a prograding and aggrading trunk stream with a thick levee deposit, and 3) peat accumulation that kept pace with relative basin subsidence are proposed mechanisms for the formation of the thick, continuous coal seams present in the basin and a disturbance or change in any of these processes could produce the splits observed in the Anderson and Canyon coal "Seams at the Antelope coal field. Syn- and post-depositional processes that have affected the coal quality and reserves at the Antelope coal field include compaction, erosion and deposition from modern stream action, and burning and oxidation of the coal seams. The position of the paleowater table during stream downcutting and erosion of the coal seams controlled the occurrence and extent of oxidation and burning. Exploration and development of the Antelope coal deposit can be executed in a more efficient manner by using the depositional model. Future exploration drilling programs, design of the mine site, mining and marketing the coal, and later reclamation of the mined area are all affected by the depositional model.

Uppermost Lance and lowermost Fort Union Formation sediments are found in outcrop in the southern portion of the Jim Bridger coal field, located on the northeast flank of the Rock Springs Uplift in Sweetwater County, Wyoming. Twenty-nine surface sections and 581 subsurface (borehole) sections were evaluated and used to construct a stratigraphic model. Stratigraphic correlations with economically mineable coal seams in the Fort Union Formation north and south of the study area combined with definition of questionable local formational boundary locations are significant objectives in this investigation.

Reflection seismic data were acquired (by CONOCO, Inc.) which targeted known channel interruption of an upper Pennsylvanian coal seam (Herrin #6) in the Illinois basin. The data were reprocessed and interpreted by the Regional Geophysics Laboratory, Virginia Tech. Conventional geophysical techniques involving field acquisition and data processing were modified to enhance and maintain high frequency content in the signal bandwidth. Single sweep processing was employed to increase spatial sampling density and reduce low pass filtering associated with the array response. Whitening of the signal bandwidth was accomplished using Vibroseis whitening (VSW) and stretched automatic gain control (SAGC). A zero-phase wavelet-shaping filter was used to optimize the waveform length allowing a thinner depositional sequence to be resolved. The high resolution data acquisition and processing led to an interpreted section which shows cyclic deposition in a deltaic environment. Complex channel development interrupted underlying sediments including the Herrin coal seam complex. Contrary to previous interpretations of channel development in the study area by Chapman and others (1981), and Nelson (1983), the channel has been interpreted as having bimodal structure leaving an"island" of undisturbed deposits. Channel activity affects the younger Pennsylvanian sediments and also the unconsolidated Pleistocene till. A limit to the eastern migration of channel development affecting the the Pennsylvanian sediments considered in this study can be identified by the abrupt change in event characteristics. / Master of Science

Attempts to recover reserves of coal situated within barrier pillars in the Beatrice Mine using the room and pillar method have thus far been largely frustrated due to magnitude, in or near the working places shortly after commencement of retreat mining in a given area. Since pillar mining offers the opportunity for achieving relatively high production at a low cost per ton the development of methods for the detection and distressing of areas of high bump probability in advance of mining would significantly improve the competitive position of the deep mines operating in the Pocahontas No. 3 seam in Buchanan County, Virginia. Unstable ground movements occurring within a panel of pillars removed using continuous mining equipment were detected using the microseismic monitoring system developed by the U. S. Bureau of Mines. Areas of high stress occurring within the panel were detected by a series of convergence points installed by the mine operator and by small diameter auger holes drilled into individual pillars. The highest levels of seismic activity were recorded during the mining of pillars which, though themselves suffering convergence to some extent, were situated inby areas in which greater amounts of closure had occurred. The presence of anomalous geologic structures in the roof strata outby, as well as the presence of pillars of irregular geometry, in close proximity to areas of high seismic occurrence was also noted. Of the pillars probed using auger drilling it was determined, using criteria developed in Poland for evaluation of bump prone pillars, that two pillars in the next panel to be mined presented an extreme hazard, while several others were of intermediate hazard potential. The practice of injecting water into pillars through holes drilled well in advance of mining was found to be largely ineffective, though injection carried out immediately following drilling of the hole in a highly stressed pillar did induce rapid convergence for a period of approximately two weeks. / M. S.